Government regulations often require fall prevention systems for roofers or others working on a roof. The requirements can vary depending on the pitch of the roof and the maximum slack in a lifeline that tethers the worker to an anchor member. Fall "restraint" systems may specify a prescribed minimum ratio, such as 4:1, of anchor strength to worker's weight for a prescribed amount of maximum slack in the lifeline. More stringent fall "arrest" regulations may for roofs of higher pitches or safety systems allowing greater freedom of the worker, i.e., greater slack in the lifeline. Regulations written specifically for roofers may be equally applicable to other workers supported on the roof after the finish roofing has been installed.
Glynn et al. U.S. Pat. No. 4,249,713, issued Feb. 10, 1981, discloses a specialized anchor formed of flat metal strap with long opposite end portions angled relative to each other to fit over the ridge of a roof understructure. Such angled end portions are intended to be positioned over inclined rafters at opposite sides of the ridge and have holes for nailing such opposite end portions to the rafters. The central portion of the anchor is return bent and has registered holes for a snap hook to which a lifeline can be attached. At the end of the roofing procedure, Glynn et al. proposed that the central portion of the anchor be bent over and covered by the ridge cap.
Jackson U.S. Pat. No. 3,237,717, issued Mar. 1, 1966, discloses a complicated safety rigging for roofers in which opposite ends of guidelines are anchored to the ground at opposite sides of a building structure.
Berry U.S. Pat. No. 742,565, issued Oct. 27, 1903, discloses a scaffold supported on an inclined roof by a "z-shaped hook" which includes one leg hooked over the ridge of the roof.
Similarly, Elkins U.S. Pat. No. 677,645, issued Jul. 2, 1901, discloses a shingler's carriage suspended from special hinged hooks which are affixed to a roof at the ridge.